Meeting Abstract

P3.117  Monday, Jan. 6 15:30  A regime shift in progress? New effects of an invasive alga in Virginia’s coastal bays BERKE, SK*; NEEDHAM, CN; SALERNO, CR; Siena College; Siena College; Siena College skberke@gmail.com

Successful invasive species have the potential to drive regime shifts in invaded ecosystems. In the coastal bays of Virginia, the invasive red alga Gracilaria vermiculophylla may now be driving such a shift. G. vermiculophyllahas represented 90% or more of all macroalgal biomass in these habitats since at least 2003. More recently, however, G. vermiculophyllahas come to form thick, continuous mats in habitats that have historically lacked algal mats. These habitats were previously dominated by the onuphid polychaete Diopatra cuprea, which has facilitated the G. vermiculophyllainvasion by attaching the algae to its tubes. Within the G. vermiculophyllamat, D. cuprea is now experiencing extraordinarily high mortality rates, evidenced by reduced abundance and by the presence of unusually large numbers of decaying tubes. The G. vermiculophyllamat is also associated with “hummocks”, mounds of sediment bound together by G. vermiculophyllaand D. cuprea tubes. Hummocks have significantly shallower oxic layers compared to nearby sediment, and are associated with high concentrations of dead D. cuprea tubes. Understanding (i) how widespread G. vermiculophyllamats are becoming, (ii) how they influence infaunal communities and sediment biogeochemical processes, and (iii) the causal link (if any) between G. vermiculophyllaand the D. cuprea die-off are important questions for future work.